The present invention relates, in general, to electrical watthour meters and, specifically, to watthour meter mounting enclosures and, more specifically to watthour meter socket adapters.
In the electric utility industry, plug-in, socket-type watthour meters are commonly employed to measure electrical power consumption at a residential or commercial building establishment. A cabinet is typically mounted on an outside wall of the residence or building and contains a meter socket having pairs of line and load contacts which are connected to electric power line conductors extending from the utility power network and electric load conductors connected to the residential or building establishment power distribution network. The contacts receive blade terminals on a plug-in watthour meter to complete an electric circuit through the meter between the line and load terminals mounted in the cabinet for the measurement of electrical power consumption.
S-type, socket-type, plug-in watthour meters have replaced older A base bottom connected meters which were formed of a single piece housing in which the watthour meter was fixedly mounted along with compression terminals which provide connection to the utility power lines and the building load distribution network.
In an installation involving an A-base bottom connected meter, an A to S socket adapter is used to allow a new S-type watthour meter to be installed. The socket type meter has outwardly extending blade terminals which are insertable into the jaw contacts in the cabinet of a S-type meter socket. The socket adapter includes its own set of female jaw contacts which receive the male blade terminals of the S-type plug-in, socket-type meter.
Although such A to S socket adapters have enjoyed widespread, reliable use over a long period of time, the Applicants devised improvements to such socket adapters as described in U.S. Pat. Nos. 5,571,031 and 5,577,933. Such improvements included a unique safety shield which completely surrounds all of the exposed portions of the jaw contacts in the socket adapter except for small slot sized to slidably receive the blade terminals of a watthour meter. In one embodiment, the safety shield is formed as an integral part of a first, front housing which is mountable in a second or rear housing to complete the socket adapter. The front and rear housings form an internal cavity within the socket adapter in which the jaw contacts, electrical conductors and terminals are disposed. The jaw contacts are received in receptacles formed in the safety shield thereby eliminating the need for separate mounting fasteners employed in previously devised socket adapters to mount each jaw terminal to the base or rear wall of the socket adapter.
Applicants also devised an improved jaw contact which minimized magnetic fields since electric currents flow from the conductors to the end of the contact clips and from the contact clips to the blade terminal of a watthour meter in the same direction. The spring clips and contact clips forming the jaw contact were affixedly secured to rigid bus bars by rivets to eliminate the need for costly threaded fasteners and apertures. The use of rigid bus bars as the electrical conductors provides a higher current carrying capacity than previously employed solid or stranded wire conductors. The jaw contacts also have a unique angular end design which substantially reduce the insertion forces required to slidably insert the blade terminals of the watthour meter into the jaw contacts; while at the same time requiring lower withdrawal forces to remove the watthour meter from the socket adapter.
The conductors employed in Applicant's prior watthour meter were installed without any external insulation since internal dividers formed on the front and rear housing provided the necessary insulation between adjacent conductors as well as the long flash distance required by electrical utility standards. Applicants' prior design also included a unique surge ground ring which terminated in a pair of mounting flanges extending from opposite ends of an angular portion to overlay a front cover filler of the front housing. A flange extends from one of the mounting flanges and passes through an aperture formed in a terminal cover before being positioned in proximity to a rim filler extension to enable a single wire seal to be passed through an aperture in the flange and an aperture in one end of a sealing ring to seal the sealing ring in the terminal cover on the watthour meter socket adapter.
Unique terminals were also disclosed in the aforementioned patents and included a collar having first and second axially extending bores. An external electrical power line load conductor is secured in the first bore of each collar by means of fasteners extendible through the collar. The second bore receives one end of one of the bus bar conductors which is in turn disposed in electrical contact with the external electrical conductor.
A unique potential jaw contact was also disclosed for use in a watthour meter socket adapter. The potential jaw contact is in the form of a three finger contact having two spaced legs extending outward from a base to which a potential lead or conductor is attached. An intermediate leg extending in an opposite angular direction from two spaced legs is disposed between the pair of legs to form a slot for receiving a blade terminal.
While Applicants' improved watthour meter socket adapter disclosed in U.S. Pat. Nos. 5,571,031 and 5,577,933 created many advances in the design of A to S watthour socket adapters, Applicants have found that further improvements could be made to Applicant's prior watthour meter socket adapter design to increase the reliability, ease of use, to improve the electrical performance characteristics of the socket adapter, as well as to reduce the manufacturing costs of the socket adapter.
Further, in previously devised watthour meter socket adapters, the insulating barriers or dividers between adjacent terminals were provided in unequal thicknesses, particularly between adjacent terminals carrying different phase line or load currents. This required special design consideration in the construction of the watthour meter socket adapter. Thus, it would be desirable to provide a terminal design for a watthour meter socket adapter which enables the spacing between adjacent terminals to equal.